Fig. 2.

Fibrillar Aβ induces FA-like structures in dystrophic neurons. Cortical neurons were treated with fibrillar Aβ at day 5, fixed at day 7, and stained with phalloidin-Texas Red, anti-Aβ, anti-paxillin (pax), and anti-integrin (int) antibodies. FAs were identified by colocalization of paxillin or integrin clusters with microfilaments.A–D, FA are absent in neurons grown on poly-l-lysine (control, PLL). Neuronal processes exhibit homogeneous distribution of paxillin and integrin, whereas microfilaments (MF, red) are primarily localized in growth cones (A, C, arrows). E, F, Neurons grown on laminin (control, Lam) exhibit paxillin and integrin clusters (arrows), associated with microfilaments periodically localized along the processes.G–J, Aβ-treated neurons on poly-l-lysine [Aβ (PLL)] develop FA-like structures proximal to Aβ fibrils (blue) that include clusters of paxillin and integrin (arrows). Microfilaments (MF, red) protruding from FA-like structures are evident in G and H (arrowheads). In some cases, growth cone filopodia appear to reverse orientation and extend toward Aβ deposits (I, J, arrowheads).K–N, Phospho-Tyr immunoreactivity (Tyr-P, green) colocalizes with paxillin (blue) and microfilaments (MF, red) in dystrophic processes (arrows). Scale bar: (in F)A–N, 5 μm. O, Quantification of integrin and paxillin clustering. Integrin receptor clustering increased 2.0 ± 0.2-fold on a laminin substrate and 1.8 ± 0.2-fold in neurons grown on poly-l-lysine after Aβ treatment. Paxillin clustering increased 3.0 ± 0.3-fold on a laminin substrate and 2.5 ± 0.3-fold in neurons grown on poly-l-lysine after Aβ treatment. Values are mean ± SEM; n = 3 independent experiments; >100 FA contacts were scored per condition; *p < 0.05 relative to control by ANOVA followed by the Student–Newman–Keulspost hoc test.